Portable transceivers that include both commercial transceivers such as cell phones and military radios have been battery powered, presently utilizing lithium battery technology to increase the time in which the battery-powered RF device can operate.
Cell phones, two-way radios, Bluetooth devices, and any number of wireless communications units having power amplifiers draw battery power based on the function of the device.
Heretofore there has been no self-adaptive configuration of the RF amplifiers as to, for instance, sense the environment and adapt the tuning associated with the final RF amplifier so that the amplifier is operating as efficiently as possible. It is of course desirable that the amplifier operate in a very linear operating region in terms of temperature and to minimize the standing wave ratio (SWR). Thus, for instance, when an individual using a handheld wireless device stands in a doorway that has a metal frame, the metal frame can detune the antenna or cause a significant mismatch in the impedance between the antenna input and the output of the RF amplifier.
Typically these wireless units are engineered without consideration of the changing environmental conditions in which they will operate; and as a result do not operate as efficiently as possible. The result is undue battery drain when the environmental conditions change at the portable device.
As to cell phones, power management capability is typically managed by the base station in which the power output is determined from the base station. In these cases there is no local tuning or other control of the cell phone RF amplifiers, which is handled externally and not intelligently by the device itself. As will be appreciated, the base station does not take into account any environmental factors such as temperature and changing SWR. Thus it is not the function of the base station to make any adjustments that would limit current drain so that the portable unit does not to run out of power.
While in the past RF transmitters have been provided with automatic antenna tuners, they are large and expensive and while they can measure standing wave ratios, they are not utilized in small handheld low-cost systems. Also the response time of the commercially available automatic antenna tuners oftentimes exceeds several seconds, which is not particularly effective in instantaneously optimizing the power amplifier/antenna portion of the transceiver.
Moreover, the algorithms utilized in automatic antenna tuners can take as many as 100,000 instructions. These sophisticated algorithms require large processors with the attendant latency and massive current consumption. Thus there is always a requirement that one conserve battery power to extend missions, and one cannot conserve battery power utilizing large processors.
There is therefore a need to optimize the RF transmitting section of a transceiver or wireless device so as not to unnecessarily impact battery resources.
What is desirable is to be able to sense the operating conditions at the amplifier and to have a feedback path by which the amplifier and its tuning circuits can be adjusted so as to optimize the RF amplifier as its operation is altered or degraded by the environmental conditions in which it finds itself. Additionally, it would be useful to be able to optimize the RF amplifier and its attendant circuitry in terms of any degradation due to circuit aging so that the RF amplifier portion of the portable device self-adjusts to minimize current drain, thus to extend battery life.
In short, there is a requirement to automatically match an RF power amplifier to a load and to ensure that optimized power is delivered to a load whilst the RF amplifier or connection to the antenna degrades due to environmental conditions.